Conditional Rendering/Occlusion Query Support

[IsaacMarovitz]

Some Xbox 360 titles, like Sonic 06, need occlusion queries and conditional rendering for accurate results.

This can be implemented performantly on D3D12 using Predication, on Vulkan using VK_EXT_conditional_rendering, and on Metal using shared visibility result buffers on UMA devices.

Every API has a slightly different take on this, which makes creating a standard abstracted API for this complex. On Vulkan, we will also need a fallback for performing a full readback of occlusion queries. While VK_EXT_conditional_rendering has good coverage on desktop platforms, it is largely unsupported on Android, and is not supported by MoltenVK.

[squidbus]

We did manage to handle our use case for this in a different way. This feature request still may be useful for others though.